a central processing unit;

real-time reproduction determination means for determining whether or not data recorded in a first recording area can be reproduced in a real-time manner;

data selection means for selecting data portions of said data recorded in said first recording area in case said data recorded in said first recording area cannot be reproduced in a real-time manner; and

relocation means for relocating said data portions selected by said data selection means to a second recording area,

wherein said data portions are relocated to the second recording area continuously in reproduction order independent of a seek operation, and

wherein the relocated data portions is data starting with a relocation start point and ending with a relocation end point, the relocation end point being defined as a piece of data selected from a first piece of data and a second piece of data,

wherein the first piece of data is defined as a piece of data to be read out from the first recording area at a point of time, at which data stored in a buffer has an amount large enough for assuring reproduction of said data in a real-time manner in an attempt to read out next data recorded in said first recording area to be reproduced after said data portions relocated to said second recording area, and

wherein the second piece of data is defined as the end point of a last relocated data portion in the second recording area, if the second recording area does not include an area large enough for accommodating another data portion to be relocated, or is defined as a piece of data, which is to be stored in the buffer at a point of time an overflow would occur in the buffer.